This invention relates to replaceable ink supply systems. More specifically, the present invention relates to expanded ink supply systems for inkjet printers generally comprising an array of detachably mounted print cartridges containing a limited amount of ink and an array of separate print heads mounted on a carriage that reciprocates across a print medium such as paper in an inkjet printer. For the purposes of this invention it is necessary to distinguish between cartridges with printheads that are affixed to a cartridge and cartridges with separate printheads.
The expanded ink supply system according to the present invention comprises a used or new cartridge for the type of printers that are equipped with separate printheads, an expanded ink supply consisting of a bag containing ink and tubing that fluidically connects  the bag to said ink cartridge. The bag is advantageously, but not necessarily, equipped with two ports for the ink of which one is used for filling and the other one for supplying the cartridge.
Ink supplies for inkjet printers with separate printheads generally consist of a cartridge equipped with a pump and a septum to intermittently supply a separate printhead via fluid conduit to a printhead filling station typically located at one end of the printer carriage's maximum stroke. Separate printheads must be protected against damage by a continuous supply of ink and therefore, ink cartridges in printers of said kind are equipped with electronic means to estimate the ink consumption and to stop a printer from working when the quantity of ink in a cartridge is estimated to be depleted or close to being depleted. A depleted cartridge is still fully functional and such cartridges are often manually refilled for continued use. The refilling procedure is time consuming and also creates objectionable stains on persons and materials. The present invention makes refilling unnecessary insomuch that the quantity of ink in the expanded ink supply system is several times the quantity in the original cartridges.
It is commonly held by persons skilled in the art that printheads should operate under negative pressure as described in U.S. Pat. No. 6,283,586. Positive printhead pressure may cause the printhead to drool. This is only of particular concern for printheads that are affixed to a cartridge, but not to printers equipped with separate printheads of the kind here described. In printers with separate printheads, overpressure conditions in the ink emanating from an external ink supply will be diminished or stopped by the cartridge's internal valve and a septum in the printhead fill station. Thus, the pressure to the printhead is unchanged and will still be regulated by the printhead pressurization mechanism.
The present invention employs continuous overpressure to prevent air ingestion into the cartridge and the fluid connections, which is beneficial to prevent air ingestion. Air that reaches the printheads may damage them severely. A liquid such as an ink solution will be more disposed to dissolve air when the solution is under negative pressure. Thus, printing systems relying on capillary action and accompanying negative pressure will be more prone to air ingestion and the printheads in such systems will deteriorate more rapidly. Another reason, according to U.S. Pat. No. 6,283,586, is that each original cartridge contains a certain amount of air and frequent cartridge replacements due to the small ink capacity of the original cartridges, the printhead air budget limit will thus be exceeded in a shorter time span than when, advantageously, expanded ink supplies of the kind described in the present invention are used. Due to prevention of air ingestion in the fluid train from the expanded ink supply up to and including the cartridge's septum and the diminished amount of air that thus may reach the printheads, according to this invention, overpressure conditions corresponding to between 50 and 200 millimeters prolong the life of printheads.
Positive pressure conditions according to the present invention are accomplished by several means. The preferred embodiment of the invention uses the force of gravity to directly feed ink from an inkbag at a higher level than the ink cartridge inside the printer. Indirect use of gravity or the use of a bag to feed a cartridge is recited in U.S. Pat. No. 5,751,319 describing an arrangement in which the cartridge is fed at a pressure substantially close to zero by employing a float valve to regulate the flow to the cartridge, while U.S. Pat. No. 5,369,429 describes a system with an ink bag where the ink cartridge is kept at sub-atmospheric pressure and the printhead and cartridge are one unit. Several inventors (U.S. Pat. No. 6,030,074 to Barinaga, U.S. Pat. No. 6,183,073 to Rottman et al. and U.S. Pat. No. 6,109,740 to Namekawa et al.) describe mechanical or fluidic pressurizing systems for a printer using a rigid container around an inner deformable bag to feed a cartridge and where the printhead and cartridge also are one unit which thus—unlike the present invention—directly pressurizes the printhead.
In an alternative embodiment of the present invention, the inkbag is pressurized by placing the printer itself over the inkbag. Typically, a printer relies on three ink colours (cyan, yellow and magenta) in addition to black ink and these inks are then stored in four separate bags. When the ink bags are pressurized by the mass of the printer itself, the inkbags according to the present invention are horizontally disposed between two surfaces of which at least one is compressible to equalize the variances in pressure in the inkbags. Using commercially available foam with a thickness of ¾″ to 1½″ as a compressible plate, a printer weighing 15–20 lbs typically forces the ink to a height 12 –18 inches above the level of the foam plate.
Pressurizing the system using gravity once the system is assembled is important. Equally important are methods described in the present invention to remove air from the expanded ink supply system during assembly. One such mechanical method according to the invention employs the forced movement of the ink through the fluid conduit to force any air to locations in the system where the air can be removed, which is described below.
The major quantity of air present in the expanded system after filling with ink is collected by allowing the ink to flow between the cartridge and the expanded ink bag in such a way that any air bubbles in the system are collected in the expanded ink bag. Most advantageously, but not necessarily, the ink bag is equipped with two openings of which one is in fluid connection with the cartridge and the other one is used for filling and also expelling visible air bubbles.
An alternative method to remove air from the system makes use of the cartridge pump and septum. By first forcing any air bubbles present in any part of the expanded ink supply system to the cartridge and then orienting the cartridge so the air is collected in close proximity to the pump channel, air can be admitted to the pump chamber by operating the diaphragm of the pump mechanism. A hollow needle is forced into the cartridge septum to allow air or air and ink mixed together to be expelled from the pump chamber when the pump's flexible diaphragm is pressed. Preferably, the hollow needle is attached to tubing and a container to collect the air/ink effluent mixture.
A method to permanently seal said fill port of the ink bag after air has been released and only ink is present in said fill port is also included in the present invention. This is accomplished by inserting suitable fittings into the ports of the bag. One of said fittings is used in the bag's fill port and is also connected to a main ink fill supply via tubing. The fittings are thermoplastically deformable so that a suitable hot tool can melt and fuse the fitting end connected to the main ink fill supply making it possible to seal the bag after air has been expelled through the fitting to the main ink fill supply and only ink is present in the fitting.
Although cartridges of the type here described have electronic means to estimate the quantity of ink remaining in a cartridge in an inkjet printer and such means are helpful when a cartridge is new, such means are of no use when used cartridges are continuously supplied from an expanded ink supply according to the present invention. Typically, a new cartridge will report that the ink level is low or the cartridge is empty when it is removed after first use from the printer as is explained in U.S. Pat. No. 6,170,937. After refilling with new ink, the cartridge's integral memory chip will still report that the ink level is the same as it was when the cartridge was removed. An empty condition will however revert to being reported as low ink condition when used for the purposes of this invention. The present invention does not rely on electronic reporting of the ink condition. Instead, simple and dependable visual means are employed. Thus, a prominent and important feature of the invention is the transparent conduit used and, optionally, the transparent casing for the original ink cartridge that both are helpful for estimating how much ink is left in the system. Also, the inkbags are advantageously, but not necessarily, transparent.
We now turn to the specific methods for gaining access to the first quantity of ink contained in the inner part of a used or new cartridge. Ink cartridges for use together with separate printheads typically have three main parts comprising firstly the inner part with the first quantity of ink in a container and pump mechanism, secondly the end cap containing the microchip for reporting the ink condition and thirdly the casing. The inner part is enclosed in the casing and the end cap. The casing and said end cap are joined together by common mechanical means and a label tape. Severing of the casing and the end cap is commonly done by removing said tape or cutting through it with a knife, both methods long known and described in early now expired patents. Therefore, such rudimentary methods to gain access to the inner part are not further described for the purposes of this invention. In a new cartridge, the cartridge's inner part fill port is in the shape of a tube blocked by an elastic body fitting the inside of the tube. Although basic and common tools are employed, such as using a threading tap or a pointed tool, methods to remove the elastic body, most often in the form of a ball, are described more recently in U.S. Pat. Nos. 6,170,937 and 6,283,586. The present invention includes a novel method to remove the elastic body from said tube by inserting a tool shaped like a fishhook's barbed end into the elastic body and then pulling it out making the cartridge inner part fill port open for insertion of a fitting.
The elbow fitting to be inserted into the cartridge's inner part fill port is most advantageously equipped with barbs for attaching tubing at one end while the fitting is threaded at the end to be screwed into the cartridge's inner part fill port. Therefore the inside of the inner part fill port must first be threaded by use of a common tap with the same thread as that of the fitting. A common sealing compound may be applied to the fitting before it is screwed into the cartridge's inner part fill port. Alternatively, an angled fitting with barbs at both ends to which optionally a common sealing compound has been applied, can be pushed into the inner part fill port. During assembly of the expanded ink supply system, for both types of fittings, flexible tubing is forced over the barbed end, pushed through an opening in the cartridge casing and then connected to the barbed end of a fitting inserted into the ink bag outlet port. The cartridge, the ink bag and the tubing now comprise the expanded ink system and is ready for filling. In a third alternative, a U-shaped fitting with barbed ends is used. One of the legs of the U is pushed into the cartridge's inner part fill port while the other leg is attached to tubing leading out of the cartridge through a hole and then connected to said ink bag.